Exploring kindergarten teachers' pedagogical content knowledge of mathematics

Last week, an interesting article was published online in the International Journal of Early Childhood. The article is entitled Exploring Kindergarten Teachers’ Pedagogical Content Knowledge of Mathematics, and it has been written by Joohl Lee. The combination of teachers knowledge of mathematics and kindergarten is very interesting, and while a lot of research has been done to learn more about the type of knowledge mathematics  teachers need in school, little has been done to learn more about this in kindergarten. This is also mentioned by Lee in the article. As the title of the article reveals, Lee builds upon Shulman's traditional framework of teachers' professional knowledge. What I don't understand, however, is how it is possible to write an article about teachers' pedagogical content knowledge of mathematics without making any reference to the MKT (Mathematical Knowledge for Teaching) framework, or any of the work done by Deborah Ball and her colleagues at the University of Michigan. I understand that this article has a focus on kindergarten, but still... I also think there should be some mention of how the teachers in the study were selected. 81 kindergarten teachers were assessed in the study, and 55% of these had a master's degree. I would like to know more about how representative this sample was. Still, I think it is an interesting article, and I think it is a good thing that the issue of kindergarten teachers' knowledge of mathematics is addressed.

Here is the abstract of the article:

The purpose of this study was to assess 81 kindergarten teachers’ pedagogical content knowledge of mathematics on six subcategory areas such as number sense, pattern, ordering, shapes, spatial sense, and comparison. The data showed participants possessed a higher level of pedagogical content knowledge of “number sense” (M = 89.12) compared to other mathematics pedagogical content areas. The second highest scores among six subcategories of pedagogical content knowledge of mathematics was for the pedagogical content area of “pattern” (M = 82.33). The lowest scores among those six subcategories of kindergarten teachers’ pedagogical content knowledge were obtained from the subcategory of “spatial sense” (M = 44.23), which involved the means to introduce children to spatial relationships. The second lowest score was obtained for the subcategory of “comparison” (M = 50.40) which involved the means to introduce the concept of graphing and the use of a balance scale for measurement.